The following relates generally to wireless communication, and more specifically to techniques for hierarchical communications in wireless communications systems.
A wireless communication network may include a number of base stations that can support communication for a number of mobile devices. A mobile device may communicate with a base station via downlink (DL) and uplink (UL) transmissions. The downlink (or forward link) refers to the communication link from the base station, such as an enhanced NodeB (eNB), to a mobile device, also referred to as a user equipment (UE). The uplink (or reverse link) refers to the communication link from the mobile device to the base station.
Multiple access technologies may use Frequency Division Duplexing (FDD) or Time Division Duplexing (TDD) to provide uplink and downlink communications over one or more carriers. TDD operation may provide relatively flexible deployments without requiring paired spectrum resources. TDD formats include transmission of frames of data, each including a number of different subframes in which different subframes may be uplink or downlink subframes. In systems that operate using TDD, different formats may be used in which uplink and downlink communications may be asymmetric. FDD operation utilizes different carriers for concurrent uplink and downlink communications.
In some wireless communication networks, base stations and UEs may support operation on multiple carriers, which may be referred to as carrier aggregation. Carrier aggregation may be used to increase throughput between a base station supporting multiple component carriers and a mobile device, and mobile devices may be configured to communicate using multiple component carriers associated with multiple base stations.
In some instances, transmission errors between mobile devices and base stations are avoided and/or corrected by utilizing an automatic repeat request (ARQ) scheme. An ARQ scheme may be employed to detect whether a received packet is in error. For example, in an ARQ scheme, a receiver may notify a transmitter with a positive acknowledgment (ACK), when a packet is received free from errors; and the receiver may notify the transmitter with a negative acknowledgment (NACK), if an error is detected. A hybrid ARQ (HARQ) scheme may be used to correct some errors and to detect and discard certain uncorrectable packets. In some scenarios, however, the overall HARQ delay may cause certain inefficiencies in wireless communications.